Found on a Property Survey – Concrete Gutters

Popular back in the sixties concrete gutters are very much of their time and in most cases past it as well. We come across them every now and then when we do a building survey and rarely if ever are they found in good working order.

The gutter system is usually known as Finlock, we understand that this was manufactured by a company called Royston to a range of designs – all broadly similar but with some changes to the detailing. The system comprises an integrated concrete gutter, lintol and eaves product that is fitted in sections of typically 200mm to 250mm width which incorporates a cavity closure at their head. (See Diagram below)

These are fitted to the top of the cavity and oversail the outer face of the wall forming the gutter. Where they pass over window openings there is a lintel tray into which the lintel sits or one is cast. Within the gutter trough a waterproof coating is applied.

There are regular problems with gutters of this type including:

An inadequate number of outlets which causes flooding and leakage. Gutters have often been lined or sealed with an asphalt or similar liquid applied product – older repairs have very often not only failed but worsened the problem as the finish is crude and uneven.

Gutters are generally laid level and are consequently extremely liable to blockage and flooding, over time the sections settle and become misaligned making this situation worse. As these sections settle the joints opening up and can start to leak, this leakage can be come apparent on the inside of the building. One also sees vertical fractures at around 240mm centres where the inner edges of opened up either by settling or usual thermal movements in the building.

There is a problem with Finlock gutters when windows are replaced, particularly when the windows are replaced by operatives inexperienced with this guttering system as they often do not realise that the gutter also forms the lintol. Typically they failed to provide adequate support and consequently misalignment can develop.

Condensation and dampness becomes evident internally typically to the upper 200 mm or so of the wall. This develops as a result of a “cold bridge”. Essentially the concrete is solid from outside to inside and so when it is cold outside the concrete sections cold inside, often used above cavity walls which were insulated or had better thermal performance the line where the concrete is at the top of the walls inside is colder than the main wall and so attracts condensation

Repair can be carried out, essentially it is a choice between lining the gutter or cutting away the protruding section of gutter and fixing a more traditional fascia board and gutter. Both methods have their benefits and will work, on balance we prefer to see them cut away rather than lined because that helps to relieve the condensation problem.

In the gallery below there are some diagrams of the system and some pictures of bungalows in Hythe, Kent. One can see typical gutter details as well as a bungalow where the gutters have been cut away and replaced.

Need a survey, homebyer report or just need to talk gutters nd problems? Give us a call 020 8295 1200

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3 Comments

Annie Steedman

January 27, 2017

Dear Steven Way

I have read your article with interest and you seem to be very knowledgeable about finlock gutters.
I am in the process of deciding whether to have my finlock gutters removed. Please would you be able to tell me if finlock gutters are made of concrete. I have asbestos downpipes.

Yes, Finlock gutters are made of concrete. Asbestos cement down pipes were quite common at the same time, you should take care when removing these and make sure they are properly disposed of at an authorised tip. If you get your contractor to ddothis ask for a copy of the disposal certificate.

Yes, Finlock gutters are made of concrete. Asbestos cement down pipes were quite common at the same time, you should take care when removing these and make sure they are properly disposed of at an authorised tip. If you get your contractor to do this ask for a copy of the disposal certificate.